1. Field of the Invention
This invention refers generally to an acceleration sensor and more specifically to a high performance fiber optic interferometric acceleration sensor.
2. Description of the Related Art
An accelerometer is typically viewed as a mass-spring transducer housed in a sensor case with the sensor case attached to a moving part whose motion is inferred from the relative motion between the mass and the sensor case. The relative displacement of the mass being directly proportional to the acceleration of the case and therefore the moving part.
One type of accelerometer is a piezoelectric based electronic accelerometer. However, it tends to suffer from several major drawbacks when faced with the continuing stricter demands of the industry. Most higher performance piezoelectric accelerometers require power at the sensor head. Also, multiplexing of a large number of sensors is not only cumbersome but tends to occur at significant increase in weight and volume of an accelerometer array.
Another type is the interferometric fiber optic accelerometers based on linear and nonlinear transduction mechanism, circular flexible disks, rubber mandrels and liquid-filled-mandrels. Some of these fiber optic accelerometers rave displayed very high acceleration sensitivity (up to 10.sup.4 radians/g), but tend to utilize a sensor design which is impracticable for many applications. For instance, sensors with a very high acceleration sensitivity typically tend to have a seismic mass greater than 500 grams which seriously limits the frequency range in which the device may be operated as an accelerometer and are so bulky that their weight and size renders them useless in many applications. Other fiber optic accelerometers suffer either from high cross-axis sensitivity or low resonant frequency or require an ac dither signal and tend to be bulky (&gt;10 kg) and expensive. For many applications, the fiber optic sensor is expected to have a flat frequency response up to several kHz (i.e., the device must have high resonant frequency), high sensitivity, be immune to extraneous measurands (e.g., dynamic pressure), be lightweight and easily configurable in an array (i.e., easy multiplexing).